Add failing tests for coverage of `GetDisplayString()`

osu.Game.Tests/Models/DisplayStringTest.cs

@@ -0,0 +1,95 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using Moq;
+using NUnit.Framework;
+using osu.Game.Beatmaps;
+using osu.Game.Extensions;
+using osu.Game.Online.API.Requests.Responses;
+using osu.Game.Rulesets;
+using osu.Game.Scoring;
+using osu.Game.Users;
+
+namespace osu.Game.Tests.Models
+{
+    [TestFixture]
+    public class DisplayStringTest
+    {
+        private static readonly object[][] test_cases =
+        {
+            new object[] { makeMockBeatmapSet(), "artist - title (author)" },
+            new object[] { makeMockBeatmap(), "artist - title (author) [difficulty]" },
+            new object[] { makeMockMetadata(), "artist - title (author)" },
+            new object[] { makeMockScore(), "user playing artist - title (author) [difficulty]" },
+            new object[] { makeMockRuleset(), "ruleset" },
+            new object[] { makeMockUser(), "user" },
+            new object[] { new Fallback(), "fallback" }
+        };
+
+        [TestCaseSource(nameof(test_cases))]
+        public void TestDisplayString(object model, string expected) => Assert.That(model.GetDisplayString(), Is.EqualTo(expected));
+
+        private static IBeatmapSetInfo makeMockBeatmapSet()
+        {
+            var mock = new Mock<IBeatmapSetInfo>();
+
+            mock.Setup(m => m.Metadata).Returns(makeMockMetadata);
+
+            return mock.Object;
+        }
+
+        private static IBeatmapInfo makeMockBeatmap()
+        {
+            var mock = new Mock<IBeatmapInfo>();
+
+            mock.Setup(m => m.Metadata).Returns(makeMockMetadata);
+            mock.Setup(m => m.DifficultyName).Returns("difficulty");
+
+            return mock.Object;
+        }
+
+        private static IBeatmapMetadataInfo makeMockMetadata()
+        {
+            var mock = new Mock<IBeatmapMetadataInfo>();
+
+            mock.Setup(m => m.Artist).Returns("artist");
+            mock.Setup(m => m.Title).Returns("title");
+            mock.Setup(m => m.Author.Username).Returns("author");
+
+            return mock.Object;
+        }
+
+        private static IScoreInfo makeMockScore()
+        {
+            var mock = new Mock<IScoreInfo>();
+
+            mock.Setup(m => m.User).Returns(new APIUser { Username = "user" }); // TODO: temporary.
+            mock.Setup(m => m.Beatmap).Returns(makeMockBeatmap);
+
+            return mock.Object;
+        }
+
+        private static IRulesetInfo makeMockRuleset()
+        {
+            var mock = new Mock<IRulesetInfo>();
+
+            mock.Setup(m => m.Name).Returns("ruleset");
+
+            return mock.Object;
+        }
+
+        private static IUser makeMockUser()
+        {
+            var mock = new Mock<IUser>();
+
+            mock.Setup(m => m.Username).Returns("user");
+
+            return mock.Object;
+        }
+
+        private class Fallback
+        {
+            public override string ToString() => "fallback";
+        }
+    }
+}